1. Field of the Invention
The invention relates to a light source module, and more particularly to a flat light source module.
2. Description of Related Art
Conventional edge-light type light emitting diode plane lamp structures usually include a light emitting diode, a light guide plate, a reflector, an optical film, or a diffusion plate. If a non-square edge-light type light emitting diode plane lamp is desired to be developed, such as a circular shaped type (the effective light emitting region is circular), since circuit boards of light bars are straight and are not flexible, and the light emitting surface of the light emitting diode needs to be parallel with the light incident surface of the light guide plate to maintain a high effective coupling rate, thus, the typical method is to design the light guide plate to be a polygon and the non-flexible circuit boards are disposed along the sides of the polygon. Then a reflector surrounds and pastes on the light exit surface of the light guide plate causing the effective light emitting region to be circular shaped, and then a front cap with a circular opening is equipped to obtain a circular light shape. This obtains a smaller effective light emitting region of the light guide plate, and a wider lamp frame.
Generally, if the light guide plate has more sides, the area of the effective light emitting region could be closer to the overall area of the light exit surface of the light guide plate (which means the area of the ineffective light emitting region may decrease) and the overall light emitting effectiveness may rise. Thus, the lamp exterior frame (ineffective region) also becomes narrower. However, the drawback is it is difficult to fabricate and the production cost is high. Even though the production cost is lowered if a quantity of light bars is decreased, sides in the effective light emitting region close to where there are no light bars are prone to form dark regions where the brightness is insufficient.
FIG. 2 of U.S. Pat. No. 7,134,768 discloses a light source apparatus of a light emitting diode. The light source apparatus includes a light guide plate and a plurality of light emitting diode light sources, wherein the light guide plate has rotational symmetry about a central axis, and the light emitting diode light sources are arranged in a circle about the central axis. In addition, FIG. 9 of U.S. patent publication No. 20090196071 discloses an illumination system. The illumination system includes a circular-shaped light guide plate and a light emitting diode light source disposed in the center of the circular-shaped light guide plate, wherein the circular-shaped light guide plate further includes a plurality of dots disposed on the surface, and a reflective layer may be disposed on the opposite surface of a light exit surface. Furthermore, FIG. 3B of U.S. patent publication No. 20040105264 discloses a light emitting diode illumination apparatus. The illumination apparatus includes a plurality of light emitting diodes, and the light emitting diodes are placed in a flexible circuit board of a soft-type board to form a light bar, wherein the light bar is placed on a curved surface.